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Título:ANALYSIS AND FORMULATION OF PROCESSES FOR TREATING LEACHATES GENERATED IN URBAN SOLIDS WASTES LANDFILLS Instituição:PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO - PUC-RIO Autor(es):GANDHI GIORDANO
Following an experimental examination of available
techniques, it was established that electrolytic treatment
and chemical precipitation are most
adequate for the primary treatment of leachates generated
in municipal solid waste landfills. It was also determined
experimentally that an air stripping operation is
indicated for removal of ammonia present in the leachate.
The initial stages of this present work concerned the
characterization of leachate in accordance with
conventional sanitary parameters, together with
analytically determined organics contents. In making such
characterizations, use was made of the leachate emanating
from the metropolitan landfill of Rio de
Janeiro (Gramacho). This leachate exhibited high
concentrations of dissolved salts, ammonia and organic
material - typical of old established landfills. Such
results are comparable with those obtained from similar
landfills in other countries. The concentration of ammonia
in the raw leachate was frequently at least 500 times the
permissible limit. Ammonia is highly toxic towards fish and
its removal is accordingly justified on these grounds alone.
Furthermore, the analyses were carried out using the
techniques of gas chromatography with mass spectrometry
(GC/MC), which permitted the identification, previously
unreported, of organic substances, originated from the
biodegradation and/or decomposition of municipal solid
wastes, and of the chemical products found in the landfill
itself or in deposited containers.
An experimental programme was, at the same time, conducted
in the laboratory to evaluate the application of the
electrolytic and chemical precipitation
processes for the treatment of leachate. A number of
diverse parameters were investigated, such as: usage of
chemicals, energy consumptions, quantity and
characteristics of sludge generated, and the quality of
treated leachate, in terms of diverse sanitary parameters.
The treated leachate was also submitted to
chromatographic analysis in order to determine changes in
its chemical composition during treatment.
The electrolytic process was shown to be well suited to the
removal of organic materials from the leachate but was not
effective in the removal of ammonia. Chemical precipitation
was found to be a suitable means of removal of
both organics and ammonia, although it does not feature
highly in terms of its cost effectiveness. A better
solution, in the overall sense, is considered to be that
which comprises a combination of these two processes.
A series of experiments was also undertaken designed to
investigate the removal of ammonia by air stripping, after
the chemical precipitation stage with calcium hydroxide.
During these experiments, the influence on the efficiency of
removal of ammonia of parameters such as pH and temperature
Removal efficiencies of the order of 90% were obtained at
pH levels between 10 and 12.5, at ambient temperature.
These experimental results indicate that the
physico-chemical processes studied represent the optimum
alternative for removal of high concentrations of
ammoniacal nitrogen encountered in leachate.
The removal of large quantities of N - NH3 is furthermore
considered to be economically attractive when followed by
biological treatment. It was also established that the
quantity of ammonia, which could be removed from the
Gramacho leachate, utilizing the stripping process, is such
as to present economic possibilities for its recovery as